The present invention relates to a method and an apparatus for packaging each of groups of cylindrical articles such as dry cells, and particularly to a method and an apparatus for sorting cylindrical articles into groups each being composed of a predetermined number of the articles, carrying the article groups in a thermal shrinkage film formed into a cylindrical shape, and cutting and heat-sealing, in the course of carrying the article groups enclosed in the cylindrical film, a boundary between a film portion enclosing one article group and a film portion enclosing the next article group.
To sort cylindrical articles such as dry cells into groups each being composed of a predetermined number of the cells and package each of the cell groups, there has been generally used a uniaxially oriented film of polyvinyl chloride being good in thermal shrinkage characteristic and transparency.
For example, Japanese Patent Examined (KOKOKU) Publication No. 53-32750 discloses a method and an apparatus in which a film of polyvinyl chloride is rewound from a film roll; during a period in which the film is carried, the film is perforated in the width direction with a predetermined pitch and is formed into a cylindrical shape with one side portion opened by a sleeve forming device; and cylindrical articles such as dry cells grouped into a predetermined number of the cells are fed in the cylindrical film. At this time, it is previously set that each group of the cylindrical articles are fed to an intermediate portion between two perforated line portions adjacent to each other in the longitudinal direction. Next, the opened edges of the opened side portion of the film are sealed in the longitudinal direction to form the film into the cylindrical shape, and then the cylindrical film is preliminarily shrunk by blasting hot-air thereto. During a period in which the preliminarily shrunk sleeve-shaped film is carried on a horizontal conveyor while being held from above and below, such a film is transferred on a slope conveyor running at a speed higher than that of the horizontal conveyor. In such transfer, the above perforated line portion is cut because the film is stretched by a difference in speed between the horizontal conveyor and the slope conveyor. After that, the packages thus separated from each other are allowed to pass through a shrink tunnel, to secondarily, perfectly shrink the film. In this way, packaged products are obtained.
In the above packaging method, even if the package has passed through the shrink tunnel, both the end portions of the package in the longitudinal direction are not perfectly sealed. If dry cells thus packaged are on display in a shopwindow for a long period of time, dust is liable to be stuck on the opened end of the dry cell package, thereby degrading the external appearance of the dry cell package.
The above-described method is suitable for packaging articles using a uniaxially oriented film of polyvinyl chloride being good in thermal shrinkage characteristic; however, it is unsuitable for packaging articles using a biaxially oriented film of low-pollution polyethylene. Since polyethylene is lower in thermal shrinkage coefficient than polyvinyl chloride and is also quite different in thermal shrinkage condition from polyvinyl chloride, a desirable packaging state cannot be obtained by using a polyethylene film if the cutting dimension of the polyethylene film is equal to that of a polyvinyl chloride film.